US7706624B2 - Apparatus and method for reducing noise in an image - Google Patents

Apparatus and method for reducing noise in an image Download PDF

Info

Publication number
US7706624B2
US7706624B2 US10567050 US56705003A US7706624B2 US 7706624 B2 US7706624 B2 US 7706624B2 US 10567050 US10567050 US 10567050 US 56705003 A US56705003 A US 56705003A US 7706624 B2 US7706624 B2 US 7706624B2
Authority
US
Grant status
Grant
Patent type
Prior art keywords
image
data
filter
signal
video
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related, expires
Application number
US10567050
Other versions
US20060245661A1 (en )
Inventor
Todd Martin Beazley
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
GVBB Holdings Sarl
Original Assignee
Thomson Licensing SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Grant date

Links

Images

Classifications

    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T5/00Image enhancement or restoration, e.g. from bit-mapped to bit-mapped creating a similar image
    • G06T5/001Image restoration
    • G06T5/002Denoising; Smoothing
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/102Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or selection affected or controlled by the adaptive coding
    • H04N19/117Filters, e.g. for pre-processing or post-processing
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/134Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
    • H04N19/136Incoming video signal characteristics or properties
    • H04N19/14Coding unit complexity, e.g. amount of activity or edge presence estimation
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/10Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
    • H04N19/169Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
    • H04N19/182Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a pixel
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/60Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using transform coding
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04NPICTORIAL COMMUNICATION, e.g. TELEVISION
    • H04N19/00Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
    • H04N19/85Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2200/00Indexing scheme for image data processing or generation, in general
    • G06T2200/24Indexing scheme for image data processing or generation, in general involving graphical user interfaces [GUIs]
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06TIMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T2207/00Indexing scheme for image analysis or image enhancement
    • G06T2207/10Image acquisition modality
    • G06T2207/10016Video; Image sequence

Abstract

An image processor includes a Lee filter for processing image data to improve noise therefrom. The Lee filter includes a smoothing control signal. During filtering of the image data, the smoothing control signal is converted to a monochrome video signal that is provided to a display instead of, or in addition to, the filtered image data. The image projected by the display of the smoothing control signal highlights edge activity in the filtered image. This display of edge activity makes it easier to locate noisy areas in the image data and fine-tune the amount of filtering to further reduce noise present in the image data and yet leave the desired image details alone.

Description

This application claims the benefit, under 35 U.S.C. § 365 of International Application PCT/US03/24525, filed Aug. 4, 2003, which was published in accordance with PCT Article 21(2) on Feb. 24, 2005 in English.

BACKGROUND OF THE INVENTION

The present invention generally relates to compression, and, more particularly, to preprocessing image data before compression to reduce the presence of noise in an image, whether a still image or a sequence of images such as in a video.

Image data is typically large in size. This is especially so if the image data represents video. As such, and as known in the art, it is preferable to compress the image data before transmission, or even storage, of the image data. In this regard, there are numerous techniques for compressing image data that to one degree or another provide some level of fidelity to the original image data.

However, when compressing image data, the image data may include noise that can adversely affect the compression efficiency since compression algorithms generally cannot distinguish noise from desired detail in the image. In other words, the size of the compressed image data may be larger than is necessary due to the presence of noise in the image data. For example, if an image is first recorded on a video cassette recorder (VCR), the recorded image data—upon playback—may now include noise. As a result, use of the VCR as a source of the image data for streaming across the Internet may, even with compression, require the use of more bandwidth than would be necessary if the noise were not present in the image data to begin with.

As such, if the image data includes noise it is known to filter the image data to first attempt to remove, or reduce, any noise before compression of the image data. Typically, one of a number of known filter techniques is applied to the image data and the filtered image data is previewed to examine the affect on the fidelity of the image. Filter settings are made by viewing the filtered image and adjusting the filter controls in an attempt to find a compromise between reduced noise and blurring of image details. Too much filtering may blur the image, too little filtering will not remove enough of the noise in the image data to improve the compression efficiency. Unfortunately, it is especially difficult to remove low-level noise that is difficult, or impossible, to see in the image but which still reduces compression efficiency. This difficulty is compounded with video, in which the image data is constantly changing.

SUMMARY OF THE INVENTION

As noted above, when filtering image data, it may be difficult to adjust the filtering to remove, e.g., low-level noise from the image data, by viewing the filtered image. However, and in accordance with the principles of the invention, I have realized that displaying where the filtering is being performed on the image data to remove noise instead of, or in addition to, displaying the filtered image data improves the ability to quickly set filter parameters to increase the removal of even low-level noise from the image data.

In an embodiment of the invention, an image processor includes Lee's local statistics filter (or Lee filter) for processing image data to remove noise therefrom. The Lee filter includes a smoothing control signal. During filtering of the image data, the smoothing control signal is converted to a monochrome video signal that is provided to a display instead of, or in addition to, the filtered image data. The displayed image representation of the smoothing control signal highlights edge activity in the filtered image. This display of edge activity makes it easier to locate noisy areas in the image data and fine-tune the amount of filtering to further reduce noise present in the image data and yet leave the desired image details alone. In particular, the display of the smoothing control signal of the Lee filter indicates light and dark areas. The dark areas indicate where the Lee filter is performing larger amounts of filtering on the image data while the brighter areas indicate where the Lee filter is performing smaller amounts of filtering on the image data.

In another embodiment of the invention, a server includes a Lee filter and a compressor for providing streaming content, e.g., video, over the Internet. The server visually displays a representation of a smoothing control signal of the Lee filter when filtering image data representing a video. The resulting displayed edge activity of the filtered image data is used to set parameters for the Lee filter, i.e., create an associated filter template for the video. The filter template is subsequently recalled for filtering the video in real-time for providing streaming video over the Internet.

In another embodiment of the invention, a server includes a Lee filter and a compressor for providing streaming content, e.g., video, over the Internet. A smoothing control signal of the Lee filter is converted to a monochrome video signal. An average brightness level for the monochrome video signal version of the smoothing control signal is set for an image or video. This set average brightness level is used to represent a desired level of filtering of the image or video. When filtering the image or video, parameters of the Lee filter are adjusted in until the average brightness level of the monochrome video signal version of the smoothing control signal substantially matches the set average brightness level.

In another embodiment of the invention, a server includes a processor, display and a memory for storing a computer program therein. The processor executes the computer program stored in the memory for filtering image data, wherein the computer program, when executed by the processor, provides a preview mode for rendering on the display where filtering is being performed on the image data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an illustrative content delivery system embodying the principles of the invention;

FIG. 2 shows in illustrative image server in accordance with the principles of the invention;

FIG. 3 show an illustrative flow chart in accordance with the principles of the invention;

FIG. 4 shows an illustrative filter preview element in accordance with the principles of the invention;

FIG. 5 shows an illustration of two preview filter operation images in accordance with the principles of the invention along with an illustrative user interface; and

FIGS. 6, 7, 8 and 9 show illustrative filter preview elements, a brightness level and a user interface in accordance with the principles of the invention.

DETAILED DESCRIPTION

Other than the inventive concept, the elements shown in the figures are well known and will not be described in detail. Also, familiarity with image processing and content delivery is assumed and is not described in detail herein. For example, other than the inventive concept, microprocessors, memory, analog and digital image formats, content streaming, media players, compression, etc., are well known and not described in detail herein. In addition, the inventive concept may be implemented using conventional programming techniques, which, as such, will not be described herein. Finally, like-numbers on the figures represent similar elements. It should also be noted that the term “signal” includes both hardware forms (e.g., electrical) and software forms (e.g., a variable). In addition, it should be noted that the use of the term “memory” below encompasses machine readable storage mediums such as, but not limited to, hard disk drives, floppy diskettes, CD-ROMS (including writable CD-ROMS), DVDs, etc.

An illustrative embodiment of a content delivery system in accordance with the principles of the invention is shown in FIG. 1. Image source 15 provides image data via signaling path 16 to image server 20 (described below), which processes the received image data to provide compressed image data via signaling path 21 for distribution to endpoints, as represented by endpoint 30, via Internet 50. The later is representative of any network capable of transmitting packets and includes switched and non-switched facilities whether wired or wireless and, as such, includes other components (not shown) such as routers and/or switches for communicating packets between an originating point and an endpoint. Image source 15 illustratively represents any source capable of providing image data, whether representing a still picture or video. For example, image source 15 may be a file source such as a hard disk drive coupled to image server 20 such that the image data represents an image, or images, in a digital format; or image source 15 may be a VCR that provides image data representing video in an analog format, etc. Likewise, although shown as a separate component not connected to Internet 50, image source 15 may also provide image data to image server 20 via Internet 50. Endpoint 30 is representative of any destination point, e.g., a consumer's video equipment, whether a computer running Windows® Media Player, or a set-top box coupled to a display; or even a server of a content provider, such as a cable company, which repackages received compressed image data as content for further distribution, e.g., to a subscriber. Likewise, image server 20 may also be a server of a content provider.

As noted earlier, when filtering image data it may be difficult to adjust parameters of the filtering operation to remove noise from the image data by just previewing the filtered image data. This is especially true in the case where low-level noise is present in the image data. As such, any noise remaining in the image data before compression may result in compressed image data that is larger in size—and that requires even more bandwidth for transmission or space for storage—than would result if the noise could be even further reduced or eliminated from the image data. Therefore, and in accordance with the principles of the invention, image server 20 displays where the filtering is performed on the image data instead of, or in addition to, displaying the filtered image data. This improves the ability to quickly set filter parameters to increase the removal of even low-level noise from the image data, thus further reducing the size of the compressed data and, concomitantly, reducing the required bandwidth for transmission or space for storage.

Turning now to FIG. 2, an illustrative high-level block diagram of an image server 20 in accordance with the principles of the invention is shown. Image server 20 is a stored-program-control based processor architecture and includes one or more processors as represented by processor 205; bus 206, which represents one or more communication paths for coupling the elements of image server 20 together; memory 210 (volatile and/or non-volatile, hard disk, CD-ROM, DVD, random access memory (RAM), etc.) for storing program instructions and data, e.g., for performing the illustrative methods described below; video processing element 220 for processing image data, which includes, in accordance with an aspect of the invention, filter preview element 225 (described below); display 230 for viewing filtered image data and, in accordance with an aspect of the invention, for viewing where the filtering is performed on the image data; and at least one receiver such as represented by communications interface(s) 215 for coupling to, e.g., video source 15, via signaling path 16 for receiving image data, and Internet 50 for transmitting compressed image data via signaling path 21. Again, it should be noted that in other embodiments of the invention image data may be provided, or sourced, in other ways, e.g., from memory 210, i.e., memory 210 becomes video source 15 in accordance with the principles of the invention. Similarly, signal path 16 may also provide a communication link to Internet 50. In addition, the image data may also be initially compressed, requiring decompression before application to filter preview element 225.

An illustrative flow chart in accordance with the principles of the invention for use in image server 20 is shown in FIG. 3. In step 305, image server 20 receives image data. The later can be either a single picture, multiple pictures, or video. In step 310, image server 20 filters the received image data to further remove noise before compression. As described further below, image server 20 illustratively uses a Lee filter as known in the art to filter the received image data. In step 315, and in accordance with the principles of the invention, image server 20 provides a preview image on display 230 (described below). This preview image visually shows where the Lee filter is operating on the received image data. In step 320, a decision is made if filter parameters of the Lee filter should be further adjusted, e.g., to remove additional noise. In this example, an operator viewing the preview image on display 230 makes the decision to adjust the filtering parameters to achieve a “perceived” level of brightness (described below) by looking at the light/dark areas of the preview image. However, as described further below, image server 20 may be programmed to automatically adjust the filter parameters in accordance with an aspect of the invention. If the filter parameters are to be adjusted, they are adjusted in step 325 and the received image data is filtered again in step 310 with the new filter parameters, etc. On the other hand, if there is to be no further adjustment to the filter parameters, then the filtered image is compressed in step 330, using any suitable compression technique as known in the art. At this point, the compressed image may be transmitted, e.g., via Internet 50, or stored for later recall.

As noted above with respect to step 315 of FIG. 3, and in accordance with the principles of the invention, a preview display capability is added to a noise reduction filter. Turning now to FIG. 4, an illustrative embodiment of a noise reduction filter having a preview display capability is shown. Filter preview element 225 includes filter 480, video converter 485 and multiplexer (mux) 490. Filter 480 illustratively implements a Lee filter as the noise reduction filter to further remove noise from image data 401 (described further below). As such, filter 480 operates on the applied image data 401 to provided filtered image data 481 to mux 490. In addition, and in accordance with an aspect of the invention, filter 480 also provides at least one filter control signal 421. The latter is converted to a video signal by video converter 485 for application to mux 490. A preview mode signal 424 further controls the operation of mux 490 to select between at least two modes of operation. In this example, it is assumed that preview mode signal 424 represents a binary form of signal where, e.g., an associated logical level of “one” corresponds to a “preview filter operation mode,” while an associated logical level of zero corresponds to a “preview filtered image mode.” It should be noted that this separation of the signals for display and the number of modes are not required for the inventive concept. For example, both the filtered image data and a filter control signal may be viewed simultaneously, e.g., within two separate windows of display 230. Further, there may be more than one display mode. However, in this example, if preview mode signal 424 represents the preview filtered image mode, then mux 490 provides filtered image data 481 as signal 426 to display 230. On the other hand, if preview mode signal 424 represents the preview filter operation mode, then mux 490 provides the video form of filter control signal 421, i.e., signal 511, as signal 426 to display 230.

A Lee filter dynamically changes the filtering process on, in effect, a pixel-by-pixel basis by measuring the amount of activity, or edge activity in small areas of the image data 401. In other words, the Lee filter examines the amount of signal activity (edge detail) in small rectangular portions (pixel windows) of an image and applies a smoothing algorithm to the center pixel of each window. The smoothing algorithm changes the amount of filtering of the center pixel as a function of edge activity within the window. Illustratively, the filter control signal 421 represents the amount of edge activity at a point in time for a particular pixel group. As such, the image developed from the filter control signal 421 pictorially shows edge activity, i.e., where filter 480 is performing noise filtering on the image data 401. Consequently, by viewing the image representative of the filter control signal 421, it is easier to both locate noisy areas in the image and fine-tune the amount of filtering to reduce the noise and leave desired image details alone. An illustration of an edge activity display is shown in FIG. 5. Both images 71 and 72 are monochrome (e.g., back and white) images of a filter control signal in accordance with the principles of the invention operating on the same image data 401. Images 71 and 72 show grayscale representations of the filter control signal 421 in which darker areas indicate where larger amounts of filtering are being performed by filter 480, while brighter areas indicate where smaller amounts of filtering are being performed by filter 480. In one illustration of the inventive concept, during the preview filter operation mode, a user observes the image of the filter control signal on display 230 and, in response thereto, adjusts a filter control signal 479 of FIG. 4 to vary the amount of filtering performed by filter 480 until a desired average brightness level is achieved on the image of the filter control signal by viewing the image of the edge activity (light areas in the images 71 and 72). In this context, image 71 has fewer light areas—hence less edge activity. Consequently, filter 480 provides a filtered image (not shown) that is not as sharp as compared to the filtered image (not shown) associated with image 72, which has more light areas, i.e., more edge activity. A user can adjust the amount of filtering by implementing a user interface, e.g., a text box, etc. An illustrative user interface for controlling the amount of filtering is shown in FIG. 5 as a slider window 85. Movement of the slider 86 from one end of the slider control 87 to the other end proportionally changes filter control signal 479 to vary the amount of filtering as, e.g., represented by images 71 and 72 of FIG. 5.

Turning now to FIGS. 6 and 7, another illustrative embodiment of filter preview element 225 is shown. Image data 401 is illustratively a multiplexed stream of luma (Y) and chroma (Cr, Cb) components of video, which are processed by filter preview element 225. As known in the art, Y represents the brightness or luminance, while Cr and Cb represent the color information (e.g., Cr corresponds to the red minus luminance signal while Cb corresponds to the blue minus luminance signal). However, in the discussion that follows, the term “pixel” is used for simplicity to describe the processing notwithstanding that the filter actually processes the Y, Cr, and Cb components separately.

Filter preview element 225 includes element 405, element 410, element 415, element 420 and mixer 425. Generally speaking, a Lee filter operates on M×L groups of pixels. For the purposes of this description, it is assumed that M=L=7. As such, each pixel group has seven rows of pixels, each row including seven pixels. Element 405 includes six line delay memories (or buffers) (not shown) such that element 405 sequentially provides rows of pixels for a particular pixel group as represented by signal 406. Element 405 also generates raster timing signal 403 as known in the art. Illustratively, row 3 of each pixel group includes the center pixel. This center pixel is also shown in FIG. 6 as signal 406-1.

In accordance with an aspect of the invention, the Lee filter is used to adaptively filter image data (whether a still picture or video). As implemented herein, the Lee filter adapts to the image data and will back off when reaching a sharp edge, i.e., an area of the image with more edge detail. The Lee filtering operates by first calculating, in element 415, the local mean of each pixel group, or window, in accordance with the following equation:

local_mean ( x _ ) = 1 N i - 1 N x i , ( 1 )
where N is the number of pixels in the filter window, and xi represents each of the pixels in the pixel group, or window. For this implementation, N=49, i.e., there are forty-nine pixels in each pixel group. Element 415 provides signal 416, which represents the local mean for a pixel group. The local mean signal 416 is applied to mixer 425 and element 410.

After the local mean of a particular pixel group is determined, element 410 calculates the variance on the same 49 pixel group in accordance with the following equation:

local_variance ( σ x 2 ) = 1 N - 1 i = 1 N ( x i - x _ ) 2 . ( 2 )
Element 410 provides signal 411, which represents the local variance for a particular pixel group to element 420. The latter determines a blend factor, β, (or smoothing control signal) in accordance with the following equation:

β = max ( σ x 2 - σ n 2 σ x 2 , 0 ) , ( 3 )
where σn 2 is a noise variance estimate and is a user-adjustable parameter to control the degree of filtering (e.g., the above-described signal 479 of FIG. 4). Element 420 provides signal 421, which is representative of the determined blend factor, β, to mixer 425. The latter determines the amount of filtering performed by the Lee filter in the preview filtered image mode in accordance with the following equation:
mixer_output=βx c+(1−β) x,  (4a)
where xc is the center pixel of the particular pixel group. Equation (4a) can be rewritten as:
mixer_output=β(x c x )+ x.  (4b)
In particular, when β has a value of zero (i.e., when the local variance is less than or equal to the estimate), mixer 425 provides maximum filtering of image data 401 (100% of the local mean is provided by mixer 425 as the filter output signal). Conversely, as the value of β increases towards one (i.e., the local variance increases above the estimate), mixer 425 provides less filtering of image data 401.

In other words, the local variance value of the Lee filter is used as a control signal that controls the mix between the local mean (i.e., the filtered center pixel) and the unfiltered center pixel. The overall amount of filtering is controlled by adjusting the value of σn 2. As local variance increases (more edge detail), the mix is changed so that more of the unfiltered center pixel is provided as the output signal of the filter. As local variance decreases (flatter regions of the image), the mix shifts in favor of the local mean, i.e., more of the filtered center pixel is provided as the output signal of the filter. As noted above, the value of σn 2 can be adjusted in any number of ways, e.g., by the above described slider window 85 of FIG. 5.

In accordance with the principles of the invention, the mixer control signal is converted to a monochrome video signal and mixer 425 provides a preview filter operation mode responsive to preview mode signal 424. The resulting preview image (again as illustrated in FIG. 5) is dark where local variance is low (i.e., where the most filtering is performed), and bright where the local variance is high (i.e., where the minimum filtering if performed).

Turning now to FIG. 7, an illustrative embodiment of mixer 425 is shown. Mixer 425 includes luma converter 505, multiplexers (muxs) 510, 515 and 520, timing and control element 525 and combination element 530. Timing and control element 525 is responsive to raster timing signal 403, described above, for controlling timing of the video signals for rendering an image on display 230. Combination element 530 implements equation (4b), above. Luma converter 505 and mux 510 convert the filter control signal 421 (β) into a monochrome video signal 511. In particular, in this illustrative implementation the preview filter operation mode shows the filtering performed on the Y samples. As such, luma converter 505 converts filter control signal 421 (β) into a luminance signal and mux 510 multiplexes this signal (under the control of timing and control element 525) with a fixed black chroma value, c (signal 509), in place of the values for Cr and Cb, thereby producing a monochrome video signal 511. Mux 515 selects between either the filtered image data 481 or the video form of filter control signal 421, i.e., signal 511, as a function of the selected mode as represented by preview mode signal 424 (described above). Mux 520 is also under the control of timing and control element 525 and selects either the output signal of mux 515 during the image portion of each video line or the center pixel (signal 406-1) during horizontal and vertical blanking intervals to preserve the synchronization and blanking signals (which are not present in signal 481 or signal 511). It should be noted that the inventive concept could easily be extended to preview Cr and Cb filtering.

The filter described above was tested with a variety of analog and digital video sources. In general, the best image improvement occurs when the noise variance estimate, σn 2, is set to low values, causing about 70% of the preview display area to be light gray or white. Increasing σn 2 to larger values increases overall filtering, and produces a higher percentage of dark gray and black areas in the preview display. Since this increases filtering of the image data, this increases the occurrence of blurred areas in the filtered image.

As described above, and in accordance with the principles of the invention, at least one control signal for a filter is converted to a video signal, which is displayed instead of, or along with, the filtered image. Adjusting the average brightness level of the image of the filter control signal provides a way to quickly adjust filter settings (e.g., the above-described noise variance estimate, a σn 2) to, e.g., reduce noise in the image data without blurring the image—thus improving any subsequent compression of the filtered image data. While the inventive concept is applicable to real-time, the filter settings, or filter template, determined in accordance with the inventive concept can also be stored, e.g., in memory 210, such that the filter template is a priori associated with particular image data and is available for future reference in filtering the image data. As such, when the particular image data is later recalled or retrieved, e.g., from video source 15, for streaming, the associated filter template is retrieved from memory 210 by processor 205 for generating the streaming image with the a priori determined amount of filtering. Whether the image data is filtered in real-time or a filter template is created for later recall, adjusting the filter settings for image data can be performed in any of a number of ways. For example, an entire video can be viewed in the “preview filter operation mode” and any settings effecting the value of the above-described noise variance estimate, σn 2, can be performed in real-time, or even recorded in real-time to produce an associated filter template for later recall. Or, a video can be sampled at different frames of the video (or even at only one frame of the video), with each sampled video frame having associated filter settings that are used for other portions of the video.

As described above, one method for adjusting the filter settings is for a user to view the image of the filter control signal and adjust the noise variance estimate to achieve a particular average brightness level. In accordance with another aspect of the invention, a target average brightness level for the image of the filter control signal can be a priori set. Once this target brightness level is set, the flow chart of FIG. 3 is modified. In particular steps 315, 320 and 325 are replaced with steps 815, 820 and 825 of FIG. 8, respectively. In step 815, the actual average brightness level for the image of the filter control signal is determined. In step 820, this actual average brightness level is compared to the target brightness level for the image of the filter control signal. If the actual average brightness level is not substantially equal to the target brightness level, then the filter is adjusted in step 825. In this regard, step 825 stores results of previous adjustments to determine in which direction to adjust the filter settings to drive the overall brightness of the image of the filter control signal to the target brightness level. Once the actual average brightness level of the image of the filter control signal is substantially equal to the target brightness level (e.g., within one percent), then step 330 of FIG. 3 is executed as described above.

It should be noted that the inventive concept can be implemented in any combination of hardware and software. For example, image server 20 can execute a computer program stored within memory 210 for providing a user interface for selection of the modes, e.g., the “preview filter operation mode” or the “preview filtered image mode,” described above. This is further illustrated in FIG. 9, which illustrates a menu-type user interface, where selection of a menu item enables the selection of a particular mode. Illustratively, selection of an “Edit Menu” 51 command further displays a list of menu items available for additional selection. These additional menu items include a command 52 (not necessarily related to the inventive concept described herein), a preview filter operation mode 53 and a preview filtered image mode 54. As such, selection, e.g., of the preview filter operation mode 53 menu item sets signal 424 to the appropriate value and provides a preview mode for rendering on display 230 where filtering is being performed on image data 401 as described above.

The foregoing merely illustrates the principles of the invention and it will thus be appreciated that those skilled in the art will be able to devise numerous alternative arrangements which, although not explicitly described herein, embody the principles of the invention and are within its spirit and scope. For example, although illustrated in the context of separate functional elements, these functional elements may be embodied on one or more integrated circuits (ICs) and/or in one or more stored program-controlled processors (e.g., a microprocessor or digital signal processor (DSP)). Further, although illustrated in the context of a Lee filter, other forms and/or combinations of filtering may be used. Similarly, although illustrated in the context of an image server, the inventive concept is applicable to any stored program controlled based system whether contained in a single piece of physical equipment (like a lap-top computer) or if distributed among a number of pieces of equipment. For example, the filtering may be performed at one computer-based terminal but the at least one control signal may be transmitted for display at another piece of equipment, whether computer-based or not. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims (25)

1. A method use in removing noise from image data, the method comprising:
receiving image data representing an image;
filtering the received image data to remove noise therefrom and to provide filtered image data; and
displaying where the filtering is being performed on the received image data.
2. The method of claim 1, further comprising the step of displaying the filtered image data.
3. The method of claim 1, further comprising the step of compressing the filtered image data to provide compressed filtered image data.
4. The method of claim 3, further comprising the step of transmitting the compressed filtered image data to an endpoint.
5. The method of claim 1, further comprising the step of, in response to the displaying step, adjusting filter parameters used in the filtering step.
6. The method of claim 5, further comprising the step of storing the adjusted filter parameters for future reference in filtering the image data.
7. The method of claim 1, wherein the filtering is performed in accordance with a Lee filter.
8. A method for use in processing image data, the method comprising:
filtering image data to provide filtered image data;
converting a control signal used in the filtering to a video signal; and
displaying an image representative of the video signal;
wherein the displayed image indicates where the image data is being filtered.
9. The method of claim 8, wherein the filtering is performed in accordance with a Lee filter.
10. The method of claim 9, wherein the control signal is a smoothing control signal of the Lee filter.
11. The method of claim 10, wherein the convening step converts the control signal to a monochrome video signal.
12. The method of claim 8, wherein the converting step converts the control signal to a monochrome video signal.
13. The method of claim 8, wherein the image is a black and white representation of edge activity in the filtered image data.
14. The method of claim 8, wherein the control signal represents a statistical function.
15. The method of claim 8, wherein the statistical function is a local variance of at least a portion of the image data.
16. The method of claim 15, wherein the portion is a group of pixels of the image data.
17. A method for use in processing image data, the method comprising:
filtering the image data to provide filtered image data in accordance with at least one value of at least one filter control signal;
converting the at least one filter control signal to a video signal;
displaying an image representative of the video signal; and
adjusting the at least one value of the at least one filter control signal in response to the displayed image.
18. The method of claim 17 wherein the adjusting step compares an average brightness level of the displayed image to a predefined average brightness level.
19. A server for processing image data, the server comprising:
a filter for filtering image data to provide filtered image data;
a video converter for converting at least one control signal of the filter to a video signal; and
a display for showing an image representative of the video signal.
20. The server of claim 19, wherein the display also shows the filtered image data.
21. A video processor comprising:
a receiver for receiving image data;
a video processing element for filtering the received image data to remove noise therefrom, wherein the video processing element includes a filter preview element for providing a video signal representative of a control signal within the video processing element; and
a display for showing an image representative of the video signal, wherein the image provides a visual indication of where noise is being removed from the image data.
22. Apparatus comprising:
a filter for filtering image data to provide filtered image data and a filter control signal;
a video converter for converting the filter control signal to a video signal; and
a display for showing an image representative of the video signal.
23. The apparatus of claim 22 further comprising:
a multiplexer coupled to the filter, video converter and the display, wherein the multiplexer is responsive to a mode control signal for coupling either the filtered image data or the video signal to the display.
24. The apparatus of claim 22, wherein the filter is a Lee filter and the control signal is a measure of a local variance of at least a portion of the image data.
25. A computer-readable medium encoded with a computer program comprising the steps of:
enabling selection of one of a number of display modes for use in processing image data, wherein at least one of the number of display modes is associated with displaying where filtering of noise in the image data is occurring; and
enabling adjustment of at least one filter control signal used in the filtering of noise in the image data.
US10567050 2003-08-04 2003-08-04 Apparatus and method for reducing noise in an image Expired - Fee Related US7706624B2 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
PCT/US2003/024525 WO2005017817A1 (en) 2003-08-04 2003-08-04 Apparatus and method for reducing noise in an image
US10567050 US7706624B2 (en) 2003-08-04 2003-08-04 Apparatus and method for reducing noise in an image

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US10567050 US7706624B2 (en) 2003-08-04 2003-08-04 Apparatus and method for reducing noise in an image

Publications (2)

Publication Number Publication Date
US20060245661A1 true US20060245661A1 (en) 2006-11-02
US7706624B2 true US7706624B2 (en) 2010-04-27

Family

ID=34192548

Family Applications (1)

Application Number Title Priority Date Filing Date
US10567050 Expired - Fee Related US7706624B2 (en) 2003-08-04 2003-08-04 Apparatus and method for reducing noise in an image

Country Status (5)

Country Link
US (1) US7706624B2 (en)
EP (1) EP1654690A4 (en)
JP (1) JP4526482B2 (en)
CN (1) CN100361141C (en)
WO (1) WO2005017817A1 (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090102918A1 (en) * 2007-06-06 2009-04-23 Olympus Corporation Microscope image pickup system
US20120038800A1 (en) * 2010-08-16 2012-02-16 Industry-University Cooperation Foundation Sogang University Method of image processing and image processing apparatus
US20170208347A1 (en) * 2015-12-23 2017-07-20 Université De Genève Image compression method with negligible and quantifiable information loss and high compression ratio
US20170372467A1 (en) * 2015-03-10 2017-12-28 Beamr Imaging Ltd Method and system of controlling a quality measure

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7522763B2 (en) * 2004-07-30 2009-04-21 Mitutoyo Corporation Method of measuring occluded features for high precision machine vision metrology
US7590303B2 (en) * 2005-09-29 2009-09-15 Samsung Electronics Co., Ltd. Image enhancement method using local illumination correction
CN101094313B (en) 2007-07-25 2011-05-18 北京中星微电子有限公司 Device and method for restraining noise
KR101678690B1 (en) * 2010-04-15 2016-11-24 삼성전자주식회사 Method for image processing and apparatus for the same
JP5758908B2 (en) * 2010-09-28 2015-08-05 パナソニック インテレクチュアル プロパティ コーポレーション オブアメリカPanasonic Intellectual Property Corporation of America Image processing apparatus, image processing method and an integrated circuit

Citations (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4238772A (en) * 1979-08-03 1980-12-09 The United States Of America As Represented By The Secretary Of The Air Force Image enhancement using on-line spatial filtering
US4908872A (en) * 1987-02-06 1990-03-13 Fujitsu Limited Method and apparatus for extracting pattern contours in image processing
US5352878A (en) * 1993-01-29 1994-10-04 United Parcel Service Of America, Inc. Method and apparatus for decoding bar code symbols using independent bar and space analysis
CN1114813A (en) 1994-04-14 1996-01-10 德克萨斯仪器股份有限公司 Motion adaptive scan-rate conversion using directional edge interpolation
US5519452A (en) * 1991-10-24 1996-05-21 Eastman Kodak Company Mechanism for improving television display of still images using image motion-dependent filter
US5682326A (en) 1992-08-03 1997-10-28 Radius Inc. Desktop digital video processing system
US5787204A (en) 1991-01-10 1998-07-28 Olympus Optical Co., Ltd. Image signal decoding device capable of removing block distortion with simple structure
US5798948A (en) * 1995-06-20 1998-08-25 Intel Corporation Method and apparatus for video filtering
US5949916A (en) * 1997-06-23 1999-09-07 Samsung Electronics Co., Ltd. Modified automatic regressive filter and filtering method therefor
US6340994B1 (en) 1998-08-12 2002-01-22 Pixonics, Llc System and method for using temporal gamma and reverse super-resolution to process images for use in digital display systems
US6389176B1 (en) 1997-09-26 2002-05-14 Trident Systems, Inc. System, method and medium for increasing compression of an image while minimizing image degradation
US6421384B1 (en) * 1997-03-20 2002-07-16 Hyundai Curitel, Inc. System and method for contour-based motion estimation
US6633342B2 (en) * 2000-01-12 2003-10-14 Lg Electronics Inc. Apparatus and method for compensating image signal
US6678009B2 (en) * 2001-02-27 2004-01-13 Matsushita Electric Industrial Co., Ltd. Adjustable video display window
US6697497B1 (en) * 1998-12-22 2004-02-24 Novell, Inc. Boundary identification and characterization through density differencing
US6697534B1 (en) * 1999-06-09 2004-02-24 Intel Corporation Method and apparatus for adaptively sharpening local image content of an image
US6947098B2 (en) * 2000-11-22 2005-09-20 Koninklijke Philips Electronics N.V. Video signal processing
US6973218B2 (en) * 2001-04-25 2005-12-06 Lockheed Martin Corporation Dynamic range compression
US7027659B1 (en) * 1998-05-20 2006-04-11 Texas Instruments Incorporated Method and apparatus for generating video images
US7046307B1 (en) * 1999-11-11 2006-05-16 Stmicroelectronics Asia Pacific Pte Ltd. Video signal noise level estimator
US7082211B2 (en) * 2002-05-31 2006-07-25 Eastman Kodak Company Method and system for enhancing portrait images

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2730363B2 (en) * 1991-12-09 1998-03-25 松下電器産業株式会社 Television receiver
JPH10294885A (en) * 1997-04-17 1998-11-04 Sony Corp Unit and method for image processing

Patent Citations (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4238772A (en) * 1979-08-03 1980-12-09 The United States Of America As Represented By The Secretary Of The Air Force Image enhancement using on-line spatial filtering
US4908872A (en) * 1987-02-06 1990-03-13 Fujitsu Limited Method and apparatus for extracting pattern contours in image processing
US5787204A (en) 1991-01-10 1998-07-28 Olympus Optical Co., Ltd. Image signal decoding device capable of removing block distortion with simple structure
US5519452A (en) * 1991-10-24 1996-05-21 Eastman Kodak Company Mechanism for improving television display of still images using image motion-dependent filter
US5682326A (en) 1992-08-03 1997-10-28 Radius Inc. Desktop digital video processing system
US5352878A (en) * 1993-01-29 1994-10-04 United Parcel Service Of America, Inc. Method and apparatus for decoding bar code symbols using independent bar and space analysis
CN1114813A (en) 1994-04-14 1996-01-10 德克萨斯仪器股份有限公司 Motion adaptive scan-rate conversion using directional edge interpolation
US5798948A (en) * 1995-06-20 1998-08-25 Intel Corporation Method and apparatus for video filtering
US6421384B1 (en) * 1997-03-20 2002-07-16 Hyundai Curitel, Inc. System and method for contour-based motion estimation
US5949916A (en) * 1997-06-23 1999-09-07 Samsung Electronics Co., Ltd. Modified automatic regressive filter and filtering method therefor
US6389176B1 (en) 1997-09-26 2002-05-14 Trident Systems, Inc. System, method and medium for increasing compression of an image while minimizing image degradation
US7027659B1 (en) * 1998-05-20 2006-04-11 Texas Instruments Incorporated Method and apparatus for generating video images
US6340994B1 (en) 1998-08-12 2002-01-22 Pixonics, Llc System and method for using temporal gamma and reverse super-resolution to process images for use in digital display systems
US6697497B1 (en) * 1998-12-22 2004-02-24 Novell, Inc. Boundary identification and characterization through density differencing
US6697534B1 (en) * 1999-06-09 2004-02-24 Intel Corporation Method and apparatus for adaptively sharpening local image content of an image
US7046307B1 (en) * 1999-11-11 2006-05-16 Stmicroelectronics Asia Pacific Pte Ltd. Video signal noise level estimator
US6633342B2 (en) * 2000-01-12 2003-10-14 Lg Electronics Inc. Apparatus and method for compensating image signal
US6947098B2 (en) * 2000-11-22 2005-09-20 Koninklijke Philips Electronics N.V. Video signal processing
US6678009B2 (en) * 2001-02-27 2004-01-13 Matsushita Electric Industrial Co., Ltd. Adjustable video display window
US6973218B2 (en) * 2001-04-25 2005-12-06 Lockheed Martin Corporation Dynamic range compression
US7082211B2 (en) * 2002-05-31 2006-07-25 Eastman Kodak Company Method and system for enhancing portrait images

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
Search Report Apr. 27, 2004.

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090102918A1 (en) * 2007-06-06 2009-04-23 Olympus Corporation Microscope image pickup system
US8233039B2 (en) * 2007-06-06 2012-07-31 Olympus Corporation Microscope image pickup system
US20120038800A1 (en) * 2010-08-16 2012-02-16 Industry-University Cooperation Foundation Sogang University Method of image processing and image processing apparatus
US8472748B2 (en) * 2010-08-16 2013-06-25 Samsung Electronics Co., Ltd. Method of image processing and image processing apparatus
US20170372467A1 (en) * 2015-03-10 2017-12-28 Beamr Imaging Ltd Method and system of controlling a quality measure
US20170208347A1 (en) * 2015-12-23 2017-07-20 Université De Genève Image compression method with negligible and quantifiable information loss and high compression ratio

Also Published As

Publication number Publication date Type
JP4526482B2 (en) 2010-08-18 grant
CN100361141C (en) 2008-01-09 grant
EP1654690A1 (en) 2006-05-10 application
US20060245661A1 (en) 2006-11-02 application
CN1820273A (en) 2006-08-16 application
EP1654690A4 (en) 2010-08-11 application
JP2007521680A (en) 2007-08-02 application
WO2005017817A1 (en) 2005-02-24 application

Similar Documents

Publication Publication Date Title
US5818975A (en) Method and apparatus for area selective exposure adjustment
US5191645A (en) Digital signal processing system employing icon displays
US6650774B1 (en) Locally adapted histogram equalization
US6154217A (en) Gamut restriction of color image
US7769089B1 (en) Method and system for reducing noise level in a video signal
US5822008A (en) Scan conversion apparatus with improved vertical resolution and flicker reduction apparatus
US5121209A (en) Sharpness control for a television image
US7317439B2 (en) Electronic apparatus and recording medium therefor
US6904169B2 (en) Method and system for improving color images
US6281933B1 (en) Images in interlaced formats: a novel method of scan conversion for video imaging systems
US20100278423A1 (en) Methods and systems for contrast enhancement
US7057664B2 (en) Method and system for converting interlaced formatted video to progressive scan video using a color edge detection scheme
US20030058464A1 (en) Tone scale adjustment of digital images
US20050152614A1 (en) Enhancing the quality of decoded quantized images
US20040131117A1 (en) Method and apparatus for improving MPEG picture compression
US20090161953A1 (en) Method of high dynamic range compression with detail preservation and noise constraints
US6903782B2 (en) System and method for performing segmentation-based enhancements of a video image
US20050013506A1 (en) Image processing method and apparatus
US20060239581A1 (en) Method and system for dynamic contrast stretch
US20090185753A1 (en) Image processing method and apparatus
US7894684B2 (en) Visual processing device, visual processing method, program, display device, and integrated circuit
US7003153B1 (en) Video contrast enhancement through partial histogram equalization
US20050168644A1 (en) Method and system for video edge enhancement
US20050180629A1 (en) Method and apparatus for processing image, recording medium, and computer program
US20050168650A1 (en) Method and system for cross-chrominance removal using motion detection

Legal Events

Date Code Title Description
AS Assignment

Owner name: THOMSON LICENSING, FRANCE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GRASS VALLEY (US) INC.;REEL/FRAME:017547/0932

Effective date: 20060111

Owner name: GRASS VALLEY (U.S.) INC., FRANCE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:BEAZLEY, TODD MARTIN;REEL/FRAME:017547/0930

Effective date: 20030821

Owner name: GRASS VALLEY (U.S.) INC.,FRANCE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:BEAZLEY, TODD MARTIN;REEL/FRAME:017547/0930

Effective date: 20030821

Owner name: THOMSON LICENSING,FRANCE

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:GRASS VALLEY (US) INC.;REEL/FRAME:017547/0932

Effective date: 20060111

AS Assignment

Owner name: GVBB HOLDINGS S.A.R.L., LUXEMBOURG

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:THOMSON LICENSING;REEL/FRAME:026028/0071

Effective date: 20101231

FPAY Fee payment

Year of fee payment: 4

FEPP

Free format text: MAINTENANCE FEE REMINDER MAILED (ORIGINAL EVENT CODE: REM.)